The bodies of many vehicles are designed with a number of pillars extending upward from the vehicle's lower structure to at least partially enclose the passenger compartment. These are sometimes referred to, starting at the front of the vehicle, as A-, B- or C-pillars, and so on. Different types of vehicles can have different numbers of pillars. One purpose of these pillars can be to guide load paths through the vehicle body, both during ordinary driving and in crash situations. FIG. 1 shows an example of load paths in a prior art vehicle 100. The vehicle body has an A-pillar 102 and a B-pillar 104 on each side thereof. The extension of each A-pillar is a roof rail 106 that extends toward the rear of the vehicle, where it meets the C-pillar. Along the way, the end of the B-pillar meets the roof rail and is attached thereto.
In the event of an impact from the side of the vehicle, the B-pillar will likely receive at least some of the load. This is here schematically illustrated using an arrow 108. In this prior art vehicle, the B-pillar uses the roof rail to transfer some of the load through the vehicle body. This is schematically illustrated using arrows 110 that represent transverse load transfer along the roof line, and arrows 112 representing longitudinal load transfer across the width of the vehicle.
FIG. 2 schematically shows a bending mode in the prior art vehicle of FIG. 1. A side sill 200 is here shown in a head-on perspective—this is the part of the vehicle's body structure that runs along the outside of the chassis on each side of the vehicle, and to which the bottom of a B-pillar 202 is attached. The B-pillar is here schematically illustrated using lines 204 that connect joints 206 to each other. The B-pillar is shown in a post-impact state, assuming that an impact load has acted on the B-pillar in a direction from right to left in the figure. The joint in the center of the B-pillar is therefore seen to have been displaced inward in the vehicle relative to a dashed line 208, which represents the undeformed state of the B-pillar. That is, the bending mode in this prior art vehicle relies on the roof rail (at the uppermost joint 206) for load transfer and has a certain intrusion of the B-pillar into the passenger compartment due to the side impact. This can reduce the effectiveness of an air bag, such as a side air bag configured to deploy in the space between a passenger and the side of the vehicle.